Fracture propagation,proppant transport and parameter optimization of multi-well pad fracturing treatment

This paper establishes a 3D multi-well pad fracturing numerical model coupled with fracture propagation and proppant migration based on the displacement discontinuity method and Eulerian-Eulerian frameworks,and the fracture propagation and proppant distribution during multi-well fracturing are investigated by taking the actual multi-well pad parameters as an example.Fracture initiation and propagation during multi-well pad fracturing are jointly affected by a variety of stress interference mechanisms such as inter-cluster,inter-stage,and inter-well,and the fracture extension is unbalanced among clusters,asymmetric on both wings,and dipping at heels.Due to the significant influence of fracture morphology and width on the migration capacity of proppant in the fracture,proppant is mainly placed in the area near the wellbore with large fracture width,while a high-concentration sandwash may easily occur in the area with narrow fracture width as a result of quick bridging.On the whole,the proppant placement range is limited.Increasing the well-spacing can reduce the stress interference of adjacent wells and promote the uniform distribution of fractures and proppant on both wings.The maximum stimulated reservoir volume or multi-fracture uniform propagation can be achieved by optimizing the well spacing.Although reducing the perforation-cluster spacing also can improve the stimulated reservoir area,a too low cluster spacing is not conducive to effectively increasing the propped fracture area.Since increasing the stage time lag is beneficial to reduce inter-stage stress interference,zipper fracturing produces more uniform fracture propagation and proppant distribution.

CifNet Network Multi-Well Data Management System

The CifNet network multi-well data management system is developed for 100MB or 1000MB local network environments which are used in Chinese oil industry. The kernel techniques of CifNet system include: 1, establishing a high efficient and low cost network multi-well data management architecture based on the General Logging Curve Theory and the Cif data format; 2, implementing efficient visit and transmission of multi-well data in C/S local network based on TCP/IP protocol; 3,ensuring the safety of multi-well data in store, visit and application based on Unix operating system security. By using CifNet system, the researcher in office or at home can visit curves of any borehole in any working area of any oilfield. The application foreground of CifNet system is also commented.

Three-dimensional physical simulation and optimization of water injection of a multi-well fractured-vuggy unit

With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil pro- duction. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fractured- vuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous （constant rate）, intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermit- tent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection-production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the devel- opment of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.

Controllable optical multi-well trap and its optical lattices using compounded cosine patterns

This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.

Numerical modeling of simultaneous hydraulic fracturing in the mode of multi-well pads

In order to investigate propagation regularity of hydraulic fractures in the mode of multi-well pads, numerical modeling of simultaneous hydraulic fracturing of multiple wells was conducted. The mathematical model was established coupling rock deformation with fluid flow in the fractures and wellbores. And then the model was solved by displacement discontinuity method coupling with implicit level set method. The implicit method was based on fracture tip asymptotical solution and used to determine fracture growth length. Simulation results showed that when multiple wells were fractured simultaneously, adjacent fractures might propagate towards each other, showing an effect of attraction other than repulsion. Fracture spacing and well spacing had significant influence on the propagation path and geometry of multiple fractures. Furthermore, when multiple wells were fractured simultaneously, stress reversal regions had a large area, and stress reversal regions were distributed not only in the area between fractures but also on the outside of them. The area of stress reversal regions was related to fracture spacing and well spacing. Results indicated that multi-well fracturing induced larger area of stress reversal regions than one-well fracturing, which was beneficial to generating complex fracture network in unconventional reservoirs.

Two-dimensional novel optical lattices with multi-well traps for cold atoms or molecules

We propose some new schemes to constitute two-dimensional （2D） array of multi-well optical dipole traps for cold atoms （or molecules） by using an optical system consisting of a binary 7r-phase grating and a 2D array of rectangle microlens. We calculate the intensity distribution of each optical well in 2D array of multi-well traps and its geometric parameters and so on. The proposed 2D array of multi-well traps can be used to form novel 2D optical lattices with cold atoms （or molecules）, and form various novel optical crystals with cold atoms （or molecules）, or to perform quantum computing and quantum information processing on an atom chip, even to realize an array of all-optical multi-well atomic （or molecular） Bose- Einstein condensates （BECs） on an all-optical integrated atom （or molecule） chip.

Self-trapping and Macroscopic Tunnelling of Superfluid Fermi Gases in Multi-well Potentials

We study the tunnelling dynamics of superfluid Fermi gases trapped in multi-well system along the BEC-BCS crossover. Within the hydrodynamical model and by using the multi-mode approximation, the self-trapping dynamics of superfluid Fermi gases in multi-well system are obtained numerically. We find that the self-trapping to diffusion transition strongly depends on the well number. When the well number is less than three, the self-trapped state takes place easier on the BEC side than that on the BCS side. However, when the well number is larger than three, the self-trapped state takes place easier on the BCS side instead of the BEC side. Furthermore, by considering a superfluid of 40K atoms, we obtain the zero-mode and π-mode Josephson frequencies of coherent atomic oscillations in double-well system. It is noteworthy that the Josephson mode, especially, the existence of π-mode frequency strongly depends on the atoms number on the BCS side.

Enhanced ionization of multi-well quantum systems in intense laser fields

The ionization dynamics of multi-well quantum systems in intense laser fields (~ 1014W/cm) has been numerically investigated through solving the time-dependent Schrodinger equation. The enhanced ionization effect at a critical inter-well distance is found as a general feature of multi-well quantum systems subjected to intense laser fields. It is well rationalized in terms of.the field-induced over-the-barriers ionization mechanism. With the number of wells increasing the whole ionization peak slightly shifts to small inter-well distance, but the enhanced ionization tendency still keeps. The ionization potential of multi-well systems is not the sole important factor of intense field-ionization of system.

威荣深层页岩储层水力压裂多井压窜现象及机理

威荣深层页岩气田五峰组—龙马溪组储层埋藏深,地质构造复杂,强非均质性天然裂缝发育,地应力高且水平地应力差大,非连续性构造在高临界应力环境下易出现扰动失稳。在储层局部连续裂缝带发育和高应力环境的共同作用下,前期400 m井距条件下出现邻井压窜和多井巷道压窜现象,导致大量生产井产能下降、续建井井壁失稳及套变问题。针对以上问题,文中基于地质-工程一体化思路,考虑了多种复杂天然裂缝分布特征和复杂裂缝扩展应力干扰效应,建立了基于DFN-FEM的井组压裂复杂裂缝扩展模型。研究发现:1)天然裂缝带和大型断裂是多井巷道压窜的主要地质因素;2)天然裂缝面法向刚度越小,压裂应力扰动范围越大,压窜越严重;3)内摩擦角和内聚力越小,岩石越容易破裂并诱发压窜;4)井组压裂顺序对压窜类型和程度均有显著影响,交错压裂最优。该研究结果可为威荣页岩储层水平井井间干扰防治与产能恢复提供依据,进而有效支撑以威荣为代表的深层页岩气田的安全高效开发。

Factors Influencing Fracture Propagation in Collaborative Fracturing ofMultiple HorizontalWells

Horizontal well-stimulation is the key to unconventional resource exploration and development.The development mode of the well plant helps increase the stimulated reservoir volume.Nevertheless,fracture interference between wells reduces the fracturing effect.Here,a 2D hydro-mechanical coupling model describing hydraulic fracture(HF)propagation is established with the extended finite element method,and the effects of several factors on HF propagation during multiple wells fracturing are analyzed.The results show that with an increase in elastic modulus,horizontal principal stress difference and injection fluid displacement,the total fracture area and the reservoir stimulation efficiency are both improved in all three fracturing technologies.After a comparison of the three technologies,the method of improved zipper fracturing is proposed,which avoids mutual interference between HFs,and the reservoir stimulation effect is improved significantly.The study provides guidance for optimizing the fracturing technology of multiple horizontal wells.

多分支废弃油井层温衰减规律及注入参数对注采性能的影响

利用废弃油井开发地热资源是降低地热开发成本、促进商业推广的有效措施,其中层温衰减规律对地热系统取热效果具有重要影响。为此,以废弃油井储层为研究对象,结合泰森多边形理论对储层裂缝进行了划分,建立了三维油水两相热流耦合数值模型,分析了不同储层条件与布井结构下的层温衰减规律,探究了注入参数等因素对地热注采性能的影响。研究结果表明:(1)低渗透储层抽采30年生产温度最大差值可达22.08 K,高渗透储层(1.0×10^(-13) m^(2))温度过度衰减,长年限采热效率低;(2)储层含油率与生产温度和发电功率呈正相关关系,生产30年后差值最大可达11.57 K与0.12 MW;(3)分支井沿垂直方向会形成低温波谷,层温衰减高于储层其余部分,数量增加对注采影响小;(4)注入速率与发电功率、生产温度分别呈正、负相关关系,但注入速率超过89 kg/s时不利于长年限开采。结论认为:(1)储层取热性能对初始渗透率最为敏感,注入速率与储层含油率次之,优先开发低渗透储层有利于长年限采热;(2)应利用油田地热降低稠油黏度,形成地热辅助采油模式,以实现经济效应最大化;(3)选取6支分支井与89 kg/s的注入速率可得到可观取热效果和较好的经济效益。

基于贝叶斯神经网络的多臂测井套损检测方法

针对传统多臂井径测井套损检测过程中,测井资料人工解释准确性不高,管柱重要信息容易遗漏等问题,结合大庆油田某工区多臂井径测井数据,提出了一种基于贝叶斯神经网络的多臂测井套损检测方法。该方法可在对原始测井曲线方位校正、缺失值填充以及对常见套损类别进行曲线数据截取汇总的基础上,形成多臂井径数据集,同时对数据集进行归一化处理并以此作为训练数据进行套损检测实验。对比发现,在多臂井径测井套损检测问题上,采用的MC Dropout变分推理方法训练的贝叶斯神经网络,相较BP神经网络、随机森林、BayesByBackprop和SGLD变分推理方法训练的贝叶斯神经网络,在性能和鲁棒性方面表现更优异。实验表明:该方法在多臂测井套损检测中有效性更高,平均准确率达到95.67%,较传统人工解释方法提升明显,并能给出可解释性更佳的分类结果不确定性,极大地提升了衡量检测结果的可信程度。

注水开发多段压裂水平井井周裂缝成像监测技术

水平井采油作为油田实现效益开发的一项重要技术,在低渗透油气田得到广泛应用。但随着生产时间延长,受井身结构及注水开发方式影响,水平井见水、水淹造成产能损失问题凸显,严重影响油田经济效益开发。对于这类水平井,缺乏成熟可靠的水平井产层生产状况测试手段,很难准确掌握水平井段主要产水原因及状况。针对这一问题,提出了井周裂缝成像监测技术,利用爬行器输送三维远场声波成像测井仪,实现对注水开发多段压裂见水水平井井周裂缝发育情况的识别,定性判识水平井段主要出水位置、来水方向及出水原因,实现快速精准找堵水,有效恢复油井产能。在长庆油田G平1井的现场应用表明,井周裂缝成像监测技术探测到该井压裂段第5、 6段井筒近端裂缝沟通明显,远场裂缝非常发育,为见水优势通道,该结果与流体扫描成像产剖测试解释结果吻合,验证了该技术的适应性。井周裂缝成像监测技术实现了精准判识出水层段及剩余油挖潜的主力层段,解决了管外窜流、层内窜流不清及后期堵水、剩余油挖潜方向不明确的难题。

基于多裂缝扩展形态的水平井压裂施工参数优化

为研究多簇压裂裂缝扩展的实际形态对水平井产能预测的影响,进而科学指导压裂施工设计,基于位移不连续法(DDM)研究了布缝间距和布缝数量2个因素对多裂缝扩展形态、流量分配的影响,并采用CMG数值模拟软件结合吉林油田H区块的实际地质参数,建立了单水平井压裂均质模型,基于产能最大化,优选出最佳的压裂施工参数。结果表明,随着簇数增加,进液量百分比极差和裂缝长度极差先增大,后略微减小;当进行4簇射孔压裂时,裂缝2、3的进液量百分比和缝宽都过小;簇间距对多裂缝扩展均匀程度有着重要影响。为了保证多裂缝扩展均匀程度更高,在实际压裂施工中应采用较大的簇间距。在H区块地层参数条件下,最优裂缝簇数为3簇,最佳簇间距为40 m,最优裂缝半长为120 m,最佳裂缝导流能力为10μm^(2)·cm。该区块适合使用黏度30 MPa·s、排量6 m^(3)/min的压裂液进行压裂。

深部地层智能压井多解性分析与优化策略

开发深部地层油气资源时普遍存在地质条件复杂、钻井周期长和井筒压力控制困难等问题,采用智能压井方法结合多源实时信息反馈,可实现井筒内气液分布状态和压力变化规律的实时预测与更新,但不同修正系数组合可能得到相同的压力计算结果,导致模型存在多解性难题。为此,分析了不同历史时间节点解空间形态的演变规律,揭示了模型多解性的本质源于少量数据约束下模型训练的不完善性;并对应建立了基于实时信息序列的模型全局训练优化方法及动态随机种群训练优化方法,测试了其对于模型全局最优解的搜索能力及适用条件。测试结果表明,全局训练优化方法在压井初期能够实现精准调控,但计算耗时较长;而动态随机种群训练优化方法在压井初期与预期值略有差异,但计算耗时较少。根据可用计算资源情况选择合适的训练优化方法,可实现多源实时数据约束下模型关于井筒气液流动规律的深度学习。

深层地热能丛式多分支U型井采热技术及传热算法

深层地热能是一种分布广、资源量大具有发展前景的可再生新能源,当前的主要开采方法有增强型地热系统(EGS)、环绕式井筒换热系统(AGS)、断层带流体循环开采和同轴套管开采法,但存在采热功率不稳定、地震风险高和采热效率低等难题。针对当前深层地热开采技术面临的瓶颈问题,本文以开采过程只有能量交换而没有物质交换为原则,以深层干热岩地热规模化可持续稳定开发为目标,提出了深层地热能丛式多分支U型井采热方法(UMW-DGS)及关键技术,在此基础上建立了井筒轴对称热传导模型,以青海共和盆地恰卜恰深部干热岩储层为背景,提出了高温高压岩石热导率测试新方法,计算了在定井径条件下井周温度场和采热功率的时空演化规律,分析了温度差、热导率和井径等3个敏感因素对采热功率的影响。此外,针对UMW-DGS定解问题,研发了基于有限体积法(FVM)的三维热流固耦合数值算法,研究了UMW-DGS单水平井段换热效率和在不同泵注量条件下温度场时空演化。通过分析不同流量的有效换热量、换热时长和功率发现:泵注流量的增加会导致有效换热能量和有效换热时长的降低,并且使有效换热功率先增加后减少。研究结果表明,深层地热能开发需要在平衡换热温度和功率的条件下设计注入排量,从而得到最优的换热效果。

面向测井领域的多模态知识图谱构建

针对测井解释过程中数据多源异构、数据间难以互补融合,不能很好应用于风险评估、解释评价和决策知识提供等问题,提出了一种面向测井领域的多模态知识图谱构建方法。该方法从测井角度出发,采用自顶向下的方式将知识整理分类为通用知识、区域知识和辅助知识等,结合测井解释过程中文本、图片、音视频等多模态资料深入挖掘实体属性关系,搭建了测井领域本体层,并基于CasRel实体关系联合抽取,余弦相似度多模态知识融合和TransR多模态表示学习技术完成了测井领域多模态知识图谱的构建。通过大庆测试服务分公司现场实际验证表明,基于该文构造的测井领域多模态知识图谱有效增强了测井知识的整合、互联和共享。

气体封隔器密封单元的增强方法与安全分析

气体封隔器胶筒是实现气井分层分段开采的关键部件。常规三胶筒结构在坐封时易发生初始破坏,导致胶筒整体应力水平降低,密封安全性储备不足。为此,提出一种多材料组合式密封单元的增强方法,用于HPHT105-232-V0型含硫化氢高温高压气体封隔器密封单元的设计;基于拉伸试验和Yeoh理论获得橡胶的本构模型参数;在温度204℃、坐封力200 kN和环空压力70 MPa下,分析了胶筒的应力和变形规律;试验测试了增强单元的密封安全性。分析结果表明:HPHT105-232-V0型封隔器密封单元胶筒的最大变形量为94.785 mm,最大接触应力为240 MPa,位于金属护环与套管接触区域。根据API标准,对HPHT105-232-V0型封隔器实物进行测试试验,坐封时胶筒未发生初始破坏,密封单元的整体应力水平提高;稳压过程胶筒压降幅度小于1%;整个试验测试过程中,密封单元无气泡溢出,封隔器卸载后胶筒结构无明显的塑性变形。研究结果表明,采用该增强方法所设计的多材料组合式密封单元具有良好的密封性能,满足极端环境下的密封安全性要求。

多分支水平井岩屑运移模型与实验研究

随着多分支水平井及复杂结构井钻井技术的不断发展,井眼清洁技术面临着新的困难和挑战。如何解决复杂地质条件与复杂井型条件下的岩屑床问题,对于判断与处理井下复杂情况是当前钻井工程面临的重要科学问题之一。通过岩屑颗粒受力分析建立了岩屑运移环空临界流速模型;基于室内可视化岩屑运移实验,探究了岩屑运移影响规律。结果表明:井斜角为36°时岩屑临界启动速度最大,携岩最为困难;模型预测结果与实验结果吻合度较好,且基于实例井的预测结果与现场作业情况一致,验证了所建模型的可靠性。该研究可为大位移大井斜井及水平井井眼清洁提供理论依据和技术支持。

基于深度强化学习的测井曲线自动深度校正方法

针对传统测井曲线深度校正需要手动调整曲线,而对于多口井的深度校正工作量巨大,需要大量人工参与,且工作效率较低的问题,提出一种多智能体深度强化学习方法(MARL)来实现多条测井曲线自动深度匹配。该方法基于卷积神经网络(CNN)定义多个自上而下的双滑动窗口捕捉测井曲线上相似的特征序列,并设计一个智能体与环境的互动机制来控制深度匹配过程。通过双深度Q学习网络(DDQN)选取一个动作来平移或缩放测井特征序列,并利用反馈的奖励信号来评估每个动作的好坏,以学习到最优的控制策略达到提升深度校正精度的目的。研究表明,MARL方法可以自动完成多口井、不同测井曲线的深度校正任务,减少人工干预。在油田实例应用中,对比分析了动态时间规整(DTW)、深度Q学习网络(DQN)和DDQN等方法的测试结果,DDQN算法采用双网络评估机制有效改进了算法的性能,能够识别和对齐测井曲线特征序列上更多的细节,具有较高的深度匹配精度。